Competing interests: RD has received honoraria for speaking and/or travelling from Biogen, Eisai, Merck, Roche and Janssen. Advisory boards for Roche, Biogen, Sandoz, Sanofi, Novartis and Merck in the past 2 years. Grant support from Biogen, Merck and Celgene. RDC has received honoraria for speaking, travelling or participating in advisory boards from Biogen, Merck, Roche, Sandoz, Sanofi, Novartis and Merck in the past 2 years. JV has received honoraria for speaking and/or travelling from Merck, Novartis and Roche. DP has received honoraria for speaking and or travelling from Biogen, Celgene, Janssen, MedDay, Merck, Novartis, Roche and Sandoz. JM has received honoraria for speaking, travelling or participating in advisory boards from Biogen, Eisai, Jannsen, Juvise, Lundbeck, Merck, Merz, Neurax, Novartis, Roche, Sandoz, Sanofi, Takeda, UCB and Zambon in the past 2 years. TA has received honoraria or consulting fees for participating in advisory boards related to trial steering committees and data and safety monitoring committees, speaker fees and research grants from Novartis, Merck, Roche, Janssen, Neuraxpharm and Sanofi-Genzyme in the past 5 years. AC is supported by the Cambridge NIHR Biomedical Research Centre and the MS Society.